#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	double s = 0;
	int sign = 1;
	for (int i = 1; i <= 100; i++)
	{
		s += (1.0 / i) * sign;
		sign *= -1;
	}
	printf("%lf", s);
	return 0;
}